Climate change will affect the population dynamics of many species, yet the consequences for the long-term persistence of populations are poorly understood. A major reason for this is that density-dependent feedback effects caused by fluctuations in population size are considered independent of stochastic variation in the environment. We show that an interplay between winter temperature and population density can influence the persistence of a small passerine population under global warming. Although warmer winters favor an increased mean population size, density-dependent feedback can cause the local population to be less buffered against occasional poor environmental conditions (cold winters). This shows that it is essential to go beyond the population size and explore climate effects on the full dynamics to elaborate targeted management actions.

In studies of partial migration, the question of interest is often approached in one of two ways. We either study the migratory process, where we typically have little or no knowledge of the breeding performance, or we study the breeding ecology and do not know exactly which individuals are migrating, dispersing or not surviving through the non-breeding season. This is due to our inability to track individuals close enough to follow them outside our window of study. With this study, we attempt to connect these two unfortunately disconnected processes of migration and breeding and thereby translate individual movement strategies into life-history ecology. Since 1973, we have studied a dipper Cinclus cinclus population in southernmost Norway. The dipper occupies a very specialized niche compared to other passerine partial migrants. It is an obligate specialist feeding on aquatic insects submerged in running fresh water. From the start of the study, individuals have been recovered abroad during winter, while others have been wintering in the study area. As all individuals are individually marked and the breeding ecology particularly well known in this system, we are able to relate movement strategies to breeding performance and survival. Ultimately, this enables us to place individual movement trajectories into a life-history context.

Nilsson, Anna (2010). To make the most of what we have – extracting phenology data from nestling measurements.
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Among the most well documented examples of climate change is the change in timing of annual events. Changes in phenology have been particularly prominent among birds. To study the ecological and evolutionary effects of climate change, scientists need access to data that has been collected over long time periods. Many long-term studies on breeding birds include detailed information about individually marked parents and offspring, but does not include information on phenology, as this often requires an even larger field effort. We demonstrate how a study of repeated standard measurements of nestlings can be used for modeling nestling growth, and how this statistical model can be used to estimate timing of breeding also for birds with sparser data. Using data from our model system of a population of white-throated dippers Cinclus cinclus in southernmost Norway, studied from 1978 until present, we also demonstrate how the extracted estimates of timing of breeding can be used for studying the ecological effects of climate change.